diff --git a/checker.go b/checker.go
index 15c3d8e..ea785c1 100644
--- a/checker.go
+++ b/checker.go
@@ -112,8 +112,9 @@ func (c *Checker) isJSON(s string) bool {
 		return false
 	}
 
-	if len(s) > 0 {
-		_, err := strconv.Atoi(s[0:1])
+	trimed := strings.TrimSpace(s)
+	if len(trimed) > 0 {
+		_, err := strconv.Atoi(trimed[0:1])
 		if err == nil {
 			return false
 		}
diff --git a/golden_test.go b/golden_test.go
index 0ad47c5..e07faa1 100644
--- a/golden_test.go
+++ b/golden_test.go
@@ -29,22 +29,24 @@ func TestDiff(t *testing.T) {
 		got     any
 		hasDiff bool
 	}{
-		"string-nodiff":       {"hello", "hello", false},
-		"bytes-nodiff":        {"hello", []byte("hello"), false},
-		"reader-nodiff":       {"hello", strings.NewReader("hello"), false},
-		"json-nodiff":         {"{\"S\":\"hello\"}\n", struct{ S string }{S: "hello"}, false},
-		"marshaler-nodiff":    {"hello", marshaler("hello"), false},
-		"empty-nodiff":        {"", "", false},
-		"number-nodiff":       {"3", "3", false},
-		"number-start-nodiff": {"3 bytes", "3 bytes", false},
+		"string-nodiff":                  {"hello", "hello", false},
+		"bytes-nodiff":                   {"hello", []byte("hello"), false},
+		"reader-nodiff":                  {"hello", strings.NewReader("hello"), false},
+		"json-nodiff":                    {"{\"S\":\"hello\"}\n", struct{ S string }{S: "hello"}, false},
+		"marshaler-nodiff":               {"hello", marshaler("hello"), false},
+		"empty-nodiff":                   {"", "", false},
+		"number-nodiff":                  {"3", "3", false},
+		"number-start-nodiff":            {"3 bytes", "3 bytes", false},
+		"number-start-with-space-nodiff": {"\n\n \n\r3 bytes", "\n\n \n\r3 bytes", false},
 
-		"string-diff":       {"Hello", "hello", true},
-		"bytes-diff":        {"Hello", []byte("hello"), true},
-		"reader-diff":       {"Hello", strings.NewReader("hello"), true},
-		"json-diff":         {"{\"S\":\"Hello\"}\n", struct{ S string }{S: "hello"}, true},
-		"marshaler-diff":    {"Hello", marshaler("hello"), true},
-		"number-diff":       {"3", "4", true},
-		"number-start-diff": {"3 bytes", "4 bytes", true},
+		"string-diff":                  {"Hello", "hello", true},
+		"bytes-diff":                   {"Hello", []byte("hello"), true},
+		"reader-diff":                  {"Hello", strings.NewReader("hello"), true},
+		"json-diff":                    {"{\"S\":\"Hello\"}\n", struct{ S string }{S: "hello"}, true},
+		"marshaler-diff":               {"Hello", marshaler("hello"), true},
+		"number-diff":                  {"3", "4", true},
+		"number-start-diff":            {"3 bytes", "4 bytes", true},
+		"number-start-with-space-diff": {"\n\n \n\r3 bytes", "\n\n \n\r4 bytes", true},
 	}
 
 	for name, tt := range cases {